Context: Intentional weight loss through dieting may adversely affect bone health. Whether testosterone treatment in men can prevent this is unknown.
Objective: To assess the effect of testosterone treatment on bone remodelling markers and bone density in dieting obese men.
Design, Setting and Participants: We conducted a pre-specified secondary analysis of a randomized double-blind, placebo-controlled clinical trial at an Academic centre. Obese men (body mass index > 30 kg/m2) with a total testosterone level <12nmol/L were enrolled.
Intervention: One hundred participants aged 53 years (interquartile range 47-60) receiving 10 weeks of a very low energy diet (VLED) followed by 46 weeks of weight maintenance were randomly assigned at baseline to 56 weeks of intramuscular testosterone undecanoate (n= 49, cases) or matching placebo (n= 51, controls). Eighty-two men completed the study.
Main outcome measures: The pre-specified outcomes were the between-group differences (mean adjusted difference, MAD) in serum c-telopeptide (CTx), N-terminal propeptide of type 1 procollagen (P1NP) and bone mineral density (BMD) at the lumbar spine and femoral neck.
At trial end, CTx was significantly reduced in men receiving testosterone compared to placebo, MAD -66ng/L (95% CI -113, -19), p=0.018, and this was apparent already after the 10 week VLED phase, MAD -63ng/L (95% CI -108, -18), p=0.018. By contrast, P1NP was marginally increased after VLED, MAD +4.2ug/L (95% CI -0.01, +8.4), p=0.057 but lower at study end, MAD -5.6ug/L (95% CI -10.1, -1.1), p=0.030 with testosterone treatment. No significant changes in sclerostin, lumbar spine BMD or femoral neck BMD were seen.
In obese men with low testosterone levels undergoing weight loss, bone remodelling is modulated in a way expected to have favourable effects in bone mass. Larger trials are required to determine whether testosterone treatment can mitigate of diet-associated bone loss.